U.S. patent number 5,615,542 [Application Number 08/451,837] was granted by the patent office on 1997-04-01 for mulching blade for lawn mower.
This patent grant is currently assigned to The Toro Company. Invention is credited to Nathan J. Friberg, Richard A. Thorud.
United States Patent |
5,615,542 |
Thorud , et al. |
April 1, 1997 |
**Please see images for:
( Certificate of Correction ) ** |
Mulching blade for lawn mower
Abstract
A cutting blade for a rotary lawn mower to increase the mulching
effectiveness of the mower comprises a generally rectangular blade
having a central portion and radially outermost end portions. The
blade is curved over its entire length to have a concavely curved
upper surface across the width thereof from one end to the other.
In addition, the radially outermost end portions of the blade are
twisted reversely relative to one another to cause the leading
edges thereof to slant downwardly as they extend from the central
portion of the blade to the tip portions of the blade.
Inventors: |
Thorud; Richard A.
(Bloomington, MN), Friberg; Nathan J. (Bloomington, MN) |
Assignee: |
The Toro Company (Minneapolis,
MN)
|
Family
ID: |
23793902 |
Appl.
No.: |
08/451,837 |
Filed: |
May 30, 1995 |
Current U.S.
Class: |
56/255; 56/295;
56/DIG.17 |
Current CPC
Class: |
A01D
34/005 (20130101); A01D 34/73 (20130101); A01D
2101/00 (20130101); Y10S 56/17 (20130101) |
Current International
Class: |
A01D
34/73 (20060101); A01D 34/00 (20060101); A01D
034/73 () |
Field of
Search: |
;56/255,295,17.5,DIG.17,DIG.20 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Toro Blade Drawing 75-9420 (Date unknown)..
|
Primary Examiner: Melius; Terry Lee
Assistant Examiner: Shackelford; Heather
Attorney, Agent or Firm: Miller; James W.
Claims
We claim:
1. A lawn mower cutting blade which is suited to be attached to a
rotatable drive means for rotating the blade about a generally
vertical rotational axis which comprises:
radially spaced apart outer blade portions located on either side
of a central blade portion, wherein each central and outer blade
portion includes a leading edge and a trailing edge taken with
reference to a forward direction of rotation of the blade, wherein
the leading edge of each outer blade portion has at least a portion
of a sharpened cutting surface for cutting the vegetation and
thereby creating vegetation clippings as the blade rotates in the
forward direction of rotation, wherein the central blade portion is
concavely curved between its leading and trailing edges when viewed
from above over a majority of its width, and wherein each outer
blade portion is twisted in a direction from the trailing edge
towards the leading edge about a longitudinal centerline of the
blade extending from the rotational axis through the outer blade
portion in a manner such that a vertical distance between reference
points on the leading and trailing edges of the outer blade
portion, measured along a transverse cross-sectional line which is
perpendicular to the centerline, progressively increases as one
moves radially outwardly along the outer blade portion.
2. A cutting blade as recited in claim 1, wherein the central blade
portion is also concavely curved between its leading and trailing
edges when viewed from above.
3. A cutting blade as recited in claim 2, wherein the degree of
concave curvature in the central blade portion is identical to the
degree of concave curvature in the outer blade portions.
4. A cutting blade as recited in claim 2, further including a
generally flat rib placed into the central portion and extending
along the centerline with the rib interrupting the concave
curvature of the central blade portion over an area covered by the
rib, the rib having openings for the reception of means for
fastening the central portion of the blade to the drive means.
5. A cutting blade as recited in claim 1, wherein the outer blade
portions each have a sail formed in the trailing edge thereof
adjacent a radially outermost tip.
6. A cutting blade as recited in claim 1, wherein the central and
outer blade portions are approximately equal in length.
7. A cutting blade as recited in claim 6, wherein the central and
outer blade portions are each approximately one third of the
blade's total length.
8. A cutting blade as recited in claim 1, wherein the sharpened
cutting edge is coextensive with most of the length of the outer
blade portion.
9. A lawn mower cutting blade which is suited to be attached to a
rotatable drive means for rotating the blade about a generally
vertical rotational axis which comprises:
a generally rectangular blade with a leading edge and a trailing
edge and having a length that substantially exceeds its width such
that the blade is elongated along a longitudinal centerline,
wherein the blade is curved across its width such that a radius of
blade curvature is defined with the radius being located above the
blade, wherein the center of the radius of blade curvature over a
central portion of the blade is aligned with a vertical reference
plane and the center of the radius of blade curvature over radially
outermost portions of the blade is substantially progressively
displaced forwardly from the vertical reference place towards a
leading edge of the blade.
10. A cutting blade as recited in claim 9, wherein the radially
outermost portions of the blade are twisted such that a leading
edge of each radially outermost portion is progressively depressed
or lowered over the length of the twisted blade portion as one
proceeds out towards a blade tip.
11. A cutting blade as recited in claim 10, wherein a sharpened
cutting edge is placed over at least a portion of each
progressively depressed leading edge.
12. A cutting blade as recited in claim 10, further including an
upwardly protruding sail formed adjacent each blade tip along a
trailing edge of each radially outermost portion.
13. A lawn mower cutting blade which is suited to be attached to a
rotatable drive means for rotating the blade about a generally
vertical rotational axis which comprises:
a generally rectangular blade with a leading edge and a trailing
edge and having a length that substantially exceeds its width such
that the blade is elongated along a longitudinal centerline,
wherein the blade includes a central portion having means for
attaching the blade to the rotatable drive means and radially
outermost portions on either side of the central portion, and
wherein the central portion of the blade is symmetrical about the
longitudinal centerline and each radially outermost portion of the
blade is concavely curved between the leading and trailing edges
and is twisted from the leading edge towards the trailing edge
relative to the longitudinal centerline in a manner causing a
leading edge of each radially outermost portion of the blade on
which a sharpened cutting edge is carried to slant substantially
uniformly downwardly relative to the longitudinal centerline over
substantially the entire length of the cutting edge.
14. A cutting blade as recited in claim 13, wherein the leading
edge of each radially outermost portion of the blade drops in a
ratio having a maximum value of approximately 1 to 10 over the
twisted blade portion.
15. A cutting blade as recited in claim 13, wherein the central
portion of the blade comprises approximately a middle one third of
the blade with the radially outermost portions of the blade each
comprising approximately a remaining one third of the blade
length.
16. A cutting blade as recited in claim 13, wherein the entire
blade is curved across the width of the blade to define a concave
upper surface when viewed from above.
17. An improved mulching rotary lawn mower of the type having at
least one cutting chamber in which a cutting blade is contained
attached to a rotatable drive means for rotating the blade about a
generally vertical rotational axis thereby establishing a generally
horizontal cutting plane, wherein the cutting chamber is generally
enclosed in a mulching mode thereof to confine the grass clippings
being circulated by rotation of the blade until such time as the
grass clippings exit the cutting chamber through an open bottom
side of the cutting chamber, the improvement relating to the blade
and comprising:
a generally rectangular blade with a leading edge and a trailing
edge and having a length that substantially exceeds its width such
that the blade is elongated along a longitudinal centerline,
wherein the blade includes a central portion having means for
attaching the blade to the rotatable drive means and radially
outermost portions on either side of the central portion, and
wherein the central portion of the blade is symmetrical about the
longitudinal centerline and each radially outermost portion of the
blade is concavely curved between the leading and trailing edges
and is twisted from the leading edge towards the trailing edge
relative to the longitudinal centerline in a manner causing a
leading edge of each radially outermost portion of the blade on
which a sharpened cutting edge is carried to slant uniformly
downwardly relative to the longitudinal centerline over
substantially the entire length of the cutting edge.
18. An improved mulching rotary lawn mower of the type having at
least one cutting chamber in which a cutting blade is contained
attached to a rotatable drive means for rotating the blade about a
generally vertical rotational axis thereby establishing a generally
horizontal cutting plane, wherein the cutting chamber is generally
enclosed in a mulching mode thereof to confine the grass clippings
being circulated by rotation of the blade until such time as the
grass clippings exit the cutting chamber through an open bottom
side of the cutting chamber, the improvement relating to the blade
and comprising:
a blade having radially spaced apart outer blade portions located
on either side of a central blade portion, wherein each central and
outer blade portion includes a leading edge and a trailing edge
taken with reference to a forward direction of rotation of the
blade, wherein the leading edge of each outer blade portion has at
least a portion of a sharpened cutting surface for cutting the
vegetation and thereby creating vegetation clippings as the blade
rotates in the forward direction of rotation, wherein the central
blade portion is concavely curved between its leading and trailing
edges when viewed from above over a majority of its width, and
wherein each outer blade portion is twisted in a direction from the
trailing edge towards the leading edge about a longitudinal
centerline of the blade extending from the rotational axis through
the outer blade portion in a manner such that a vertical distance
between reference points on the leading and trailing edges of the
outer blade portion, measured along a transverse cross-sectional
line which is perpendicular to the centerline, progressively
increases as one moves radially outwardly along the outer blade
portion.
19. An improved mulching rotary lawn mower of the type having at
least one cutting chamber in which a cutting blade is contained
attached to a rotatable drive means for rotating the blade about a
generally vertical rotational axis thereby establishing a generally
horizontal cutting plane, wherein the cutting chamber is generally
enclosed in a mulching mode thereof to confine the grass clippings
being circulated by rotation of the blade until such time as the
grass clippings exit the cutting chamber through an open bottom
side of the cutting chamber, the improvement relating to the blade
and comprising:
a generally rectangular blade having a leading edge and a trailing
edge and a length that substantially exceeds its width such that
the blade is elongated along a longitudinal centerline, wherein the
blade is curved across its width such that a radius of blade
curvature is defined with the radius being located above the blade,
wherein the center of the radius of blade curvature over a central
portion of the blade is aligned with a vertical reference plane and
the center of the radius of blade curvature over radially outermost
portions of the blade is substantially progressively displaced
forwardly from the vertical reference place towards a leading edge
of the blade.
20. A cutting blade as recited in claim 19 wherein the longitudinal
centerline of the blade is contained within the vertical reference
plane.
21. A cutting blade as recited in claim 9, wherein the longitudinal
centerline of the blade is contained within the vertical reference
plane.
Description
TECHNICAL FIELD
This invention relates to a cutting blade for a rotary lawn mower
which blade is shaped for efficiently hiding or depositing the
grass clippings in the cut grass path, namely for enhancing the
mulching effectiveness of the lawn mower.
BACKGROUND OF THE INVENTION
Mulching lawn mowers are known which direct the grass clippings
severed by the cutting blade downwardly out of the cutting chamber
to deposit such clippings in the standing grass remaining in the
cut grass path. Various kinds of such mulching mowers are known.
For example, mulching mowers are disclosed in U.S. Pat. Nos.
4,205,512 and 4,951,449 to Thorud, both of which are assigned to
the assignee of this invention.
The mulching mowers shown in the Thorud patents have grass
deflecting members or kickers within the cutting chamber to assist
in the downward movement of the grass clippings. These kickers
comprise angled grass deflecting surfaces that are fixed in each
cutting chamber above the plane of the blade. The grass deflecting
surfaces are shaped and positioned to intercept the grass clippings
as they circulate inside the cutting chamber to redirect such
clippings downwardly. The kickers are spaced apart around the
circumference of the cutting chamber.
Other mulching mowers are known in which no kicker members are
present in the cutting chamber. Instead, the cutting chamber and
blade are specially shaped to effect mulching. For example, U.S.
Pat. No. 3,085,386 to Slemmons discloses a mulching mower having a
donut-shaped cutting chamber. A specially configured cutting blade
allegedly causes the grass clippings to be cut in a radial outer
portion of the cutting chamber and to be circulated upwardly and
inwardly inside the cutting chamber to eventually be driven
downwardly out of the cutting chamber through a radial inner
portion of the chamber.
SUMMARY OF THE INVENTION
It is one aspect of this invention to provide a uniquely shaped
blade for a rotary lawn mower which provides a good quality of cut
and superior mulching as compared to known prior art blades.
One aspect of this invention relates to a lawn mower cutting blade
which is suited to be attached to a rotatable drive means for
rotating the blade about a generally vertical rotational axis. The
blade is generally rectangular having a length that substantially
exceeds its width such that the blade is elongated along a
longitudinal centerline. The blade is curved across its width
extending the length of the blade such that the blade has a concave
upper face and a convex lower face. Radially outermost portions of
the blade are twisted reversely relative to one another about the
longitudinal centerline.
BRIEF DESCRIPTION OF THE DRAWINGS
This invention will be described hereafter in the Detailed
Description, taken in conjunction with the following drawings, in
which like reference numerals refer to like elements or parts
throughout.
FIG. 1 is a front elevational view of an improved mulching blade
according to this invention shown installed on a rotary lawn
mower;
FIG. 2 is a larger front elevational view of the blade shown in
FIG. 1;
FIG. 3 is a top plan view of the blade shown in FIG. 1;
FIG. 4 is a longitudinal cross-sectional view along the
longitudinal centerline of the blade taken along lines 4-4 in FIG.
3;
FIGS. 5-16 are transverse cross-sectional views of the blade shown
in FIG. 1 taken along transverse cross-sectional lines that are
spaced apart along the longitudinal centerline of the blade from
the center of the blade to one tip thereof, with FIG. 5 being taken
along lines 5--5 of FIG. 2, FIG. 6 being taken along lines 6--6 of
FIG. 2, and so on.
DETAILED DESCRIPTION
The improved mulching blade of this invention is generally
illustrated in FIG. 1 as 2. Blade 2 is mounted in a mulching lawn
mower 4 having a housing or cutting deck 6 supported for movement
over the ground in any suitable manner, e.g. by a plurality of
ground engaging wheels 8. Deck 6 includes at least one cutting
chamber 10 for containing and enclosing rotatable cutting blade 2.
Blade 2 is generally horizontal within cutting chamber 10 to rotate
in a generally horizontal cutting plane about a generally vertical
rotational axis.
A generally circular cutting chamber 10 is provided in deck 6
having a peripheral side wall 12 and a top wall 14 for enclosing
blade 2. The bottom side of this cutting chamber is substantially
open and faces the ground when lawn mower 4 is placed upright as
shown in FIG. 1. Cutting chamber 10 is substantially enclosed to
prevent the grass clippings from exiting cutting chamber 10 except
through the open bottom side of cutting chamber 10, thus causing
mower 2 to be a "mulching mower". In this regard, the term mulching
mower is intended to cover mowers which are convertible between a
mulching mode and a grass discharge/collection mode in which the
grass clippings can exit cutting chamber 10 through a selectively
openable grass discharge outlet in side wall 12 or top wall 14, as
long as such mower has at least one mode or configuration in which
side wall 12 and top wall 14 are substantially enclosed (i.e. the
grass discharge outlet is blocked) to cause the clippings to be
driven downwardly out of chamber 10 through the open bottom side of
the chamber.
The exact details of the lawn mower and cutting chamber 10 are not
important to this invention as long as some type of enclosed
cutting chamber having a generally open bottom side surrounds and
encloses blade 2. This invention relates to a novel and uniquely
shaped cutting blade 2 that enhances the mulching effectiveness of
such a mower. Thus, in FIG. 1, mower 4 and cutting chamber 10 are
diagrammatically shown in phantom so as not to obscure cutting
blade 2.
Referring now to FIG. 3, cutting blade 2 is generally rectangular
having a length that substantially exceeds its width such that
blade 2 is elongated along a longitudinal centerline 15 located in
the upper face 24 of blade 2. Blade 2 is provided with sharpened
cutting edges 16 along opposite longitudinal edges of blade 2 and
adjacent opposite ends of blade 2. Blade 2 is formed to have
generally identical left and right halves 18. Each cutting blade
half 18 has a leading edge 20 and a trailing edge 22 spaced apart
by the width of blade 2 taken with respect to the normal forward
direction of blade 2 as represented by the arrows A in FIG. 3. Each
cutting edge 16 of blade 2 is located on the leading edge 20 of one
blade half 18. Each cutting edge is approximately 6 inches long in
an approximately 20.6 inch long blade as measured along centerline
15.
Cutting blade 2 of this invention is generally uniformly curved or
cupped across its width extending the length of blade 2. Thus, if
one were to orient blade 2 horizontally with the curve facing
upwardly as is the case during use of blade 2, blade 2 would have a
shallow concave shape along the length thereof when viewed from
above and a shallow convex shape when viewed from below. Thus, as
shown in FIG. 6, blade 2 has a concave upper face 24 and,
correspondingly, a convex lower face 26.
The generally uniform curve occurring across the width of blade 2
has two exceptions. First, a central flattened rib 28 is placed
into blade 2 over the central portion of blade 2 with such flat rib
28 having at least one opening 30 through which fastener(s) can
pass for attaching blade 2 to the drive shaft 31 of an internal
combustion engine or other motor. Thus, as shown in FIG. 5, the
curve in blade 2 is interrupted by the flat rib 28 over the length
of rib 28. Flat rib 28 is also approximately 6 inches long in an
approximately 20.6 inch long blade 2 as measured along centerline
15. However, since the width of rib 28 is preferably less than the
width of blade 2, the concave upper face 24 and convex lower face
26 of blade 2 remain on either side of rib 28, i.e. the curve in
blade 2 is still present even along the central portion of blade 2
but is just interrupted by the presence of flat rib 28.
While rib 28 is desirably used in blade 2 for more easily securing
blade 2 to the drive shaft 31 in many lawn mowers 4, it could be
deleted from blade 2 without departing from this invention. In such
a case, the generally uniform curve in blade 2 would be undisturbed
over the central portion of blade 2.
The second exception to the generally uniform curve in blade 2
involves the formation of a sail 32 at each tip 34 of blade 2 at
the trailing edge 22 of each blade half 18. Basically, a triangular
section of blade 2 is bent or further curved upwardly relative to
concave upper surface 24 along a line 36 which is inclined relative
to centerline 15 to form sail 32. Obviously, the smooth, generally
uniform curve that previously existed in blade 2 is now disrupted
in the area of sail 32. Thus, on each transverse cross-section
taken through the width of blade 2 passing through a portion of
sail 32, there are now effectively two curved sections, one having
a radius rb representing the radius of the concave upper face 24 in
blade 2 and the other having a radius rs representing the radius of
upper face 24 in sail 32.
If blade 2 were shaped only as described above, the curve in blade
2 would, in effect, form a shallow concave trough over its length.
A drop of water placed on any transverse cross-sectional line could
not travel along the transverse cross-sectional line and escape
from the trough, but rather would tend to flow down the curve of
the transverse cross-sectional line to a lowermost point along the
line, normally where the transverse cross-sectional line intersects
centerline 15.
However, blade 2 of this invention includes one additional design
feature. The radially outermost portions of blade 2 on either side
of the central portion are twisted about longitudinal centerline 15
so that each blade half 18 also twists forwardly towards its
leading edge 20 over such radially outermost portions. Each leading
edge 20 is progressively depressed or lowered over the length of
the twisted blade portion as one proceeds out towards blade tip
34.
In attempting to visualize the twist imparted in blade 2, imagine
taking a uniformly curved blade 2 prior to the twist and holding
such blade in front of your body with one hand on each end of the
blade near the tip and specifically with your left hand being on
that end of the blade in which cutting edge 16 of the blade faces
away you and your right hand being on that end of the blade in
which cutting edge 16 faces towards you. Then, imagine simply
twisting each half of the blade reversely relative to one another
about longitudinal centerline 15 of the blade, i.e. you would twist
away from your body with your left hand and twist towards your body
with your right hand.
The effect of twisting blade 2 in the manner described above is
graphically illustrated in FIGS. 5-16 which show a plurality of
transverse cross-sectional views spaced apart along longitudinal
centerline 15 of the blade from the center of the blade to one tip
thereof. An xy coordinate system having its origin placed on the
blade centerline is superimposed onto each of these views and is
constant. Any deviation in the position of blade 2 in reference to
the xy coordinate system is due to the twist in the radially
outermost portions of blade 2.
FIG. 5 is a view taken through the center of blade 2 and
illustrates flat rib 28 placed into blade 2. FIG. 6 is a view taken
through a central portion of blade 2 just immediately past one end
of rib 28 and somewhat before sharpened cutting edge 16 begins.
Referring to both of these figures, one can see that the twist in
blade 2 has not yet begun. Clearly, the center of the radius rb of
the blade curvature is still aligned with the y axis of the xy
coordinate system with the leading and trailing edges 20, 22 of the
blade cross-section being symmetrically located above the x
axis.
However, at some point past the end of rib 24 slightly beyond the
cross-section of FIG. 6 and thus before the beginning of the
sharpened cutting edge 16, the twist previously described for blade
2 preferably begins. The first cross-section for which the twist is
shown, namely FIG. 7, is somewhat radially inboard of cutting edge
16 with the next cross-section, FIG. 8, being radially aligned with
the beginning of cutting edge 16. As the twist begins and
progressively takes effect, the center of the radius rb of the
blade curvature progressively translates forwardly of the y axis in
the -x direction and leading edge 20 of blade half 18 progressively
drops down or depresses relative to the x axis in the -y direction.
As one proceeds radially out towards tip 34 along longitudinal
centerline 15 from one transverse cross-section to the next, one
can easily see this progressive translation of these blade
reference points relative to the xy axes. For example, referring to
FIG. 16, note how far leading edge 20 has dropped along the y axis
and how far the center of the radius rb has moved in front of the y
axis along the x axis.
A similar translation will also occur for the center of the radius
rs of the sail curvature as shown in FIGS. 13-16. Beginning with
FIG. 13, which is a cross-section taken at the very beginning of
the sail, the sail curvature radius rs will have the its center at
a predetermined initial position. As the twist in blade 2 proceeds
out towards tip 34, the center of radius rs also moves
progressively forwardly in the -x direction from its initial
position shown in FIG. 13 to its final position shown in FIG.
16.
The effect of the blade twist described above is to open up the
shallow concave trough formed in blade 2 over the radially
outermost twisted portions of the blade with leading edge 20
progressively dropping down relative to trailing edge 22. Thus, to
use the earlier example of a drop of water placed along a
transverse cross-sectional line, such a drop of water now placed
along one of the radially outermost transverse cross-sectional
lines will now flow down the line and towards and over leading edge
20 which is now the lowermost point along the line. See FIGS.
14-16. The radially outermost portions of blade 2 which have been
twisted are now sloped downwardly relative to the central portion
along the longitudinal centerline 15. See the cross-section shown
in FIG. 4 and the angle of slope denoted as .alpha..
The distance between the cross-sections taken along lines 5--5 and
6--6 is 3 inches, corresponding to one half of the length of rib
28. The distance between adjacent ones of the cross-sections taken
along lines 6--6 through 16--16 is a uniform 0.75 inches, with the
exception that the cross-section taken along lines 14--14 is an
intermediate cross-section spaced 0.45 inches from the
cross-section taken along lines 13--13 and 0.30 inches from the
cross-section taken along lines 15--15. Thus, the distance from the
cross-section taken along lines 8--8, which is aligned with the
start of sharpened cutting edge 16, to the cross-section taken
along lines 16--16, which is quite close to tip 34 and near the end
of sharpened cutting edge 16, is 5.25 inches.
Referring to FIG. 6, one can see that the leading and trailing
edges 20 and 22 are vertically aligned with each other before the
twist begins. As blade 2 twists and leading edge 20 is depressed
relative to the y axis, leading edge 20 will progressively drop
below trailing edge 22 to pass through the 0 value of y and
eventually reach a -y value while trailing edge 22 will always stay
at a slight +y value. The amount of such drop measured along
leading edge 20 is 0.461 inches in the 5.25 inches between the
cross-sections taken along lines 8--8 and 16--16, respectively, or
approximately 0.09 inches of drop for each inch length of twist
normally angular along the length of cutting edge 16, i.e. a ratio
having a maximum value of approximately 1 to 10 over the twisted
blade portion.
Blade 2 can be thought of as being divided approximately into
thirds. There is a middle third which forms the central portion of
the blade, namely that portion having rib 28, which is not-twisted
but is symmetrical about the xy coordinate system. In addition,
blade 2 has radially outer thirds having cutting edges 16 extending
along a leading edge thereof. The radial outer thirds are twisted
about the longitudinal centerline 15 in a manner causing the
leading edge on which the sharpened cutting edge is carried to
slant uniformly downwardly over the entire length of cutting edge
16. Short connecting sections serve to connect the middle and outer
thirds of blade 2, namely those portions of blade 2 between the end
of rib 28 and the start of a cutting edge 16.
Blade 2 has been found by the Applicants to have superior mulching
ability and a good quality of cut. In tests of blade 2, grass is
cut cleanly and evenly and the grass clippings created by blade 2
are well hidden in the cut grass path, even when cutting long, wet
grass.
The mulching effectiveness of blade 2 is apparent even when blade 2
is used without other means for enhancing the mulching ability of
mower 4. However, blade 2 can also be used in a mower having a
plurality of grass deflecting members mounted in cutting chamber 10
as taught by U.S. Pat. No. 4,951,449 to Thorud, which patent is
hereby incorporated by reference. Additionally, a set of rotating
winglets can be bolted to the underside of blade as taught in U.S.
Pat. No. 5,363,635 to White et al., which patent is also hereby
incorporated by reference.
Blade 2 is preferably manufactured in any appropriate manner from a
rigid metallic material such as steel. For example, blade 2 could
be manufactured by first placing the concave curve into a flat
blank, by then stamping rib 28 into the blade and by bending sails
32, and by then physically twisting the radially outermost portions
of blade 2. Alternatively, blade 2 could be integrally cast or
molded from a form having the requisite shape therein.
Various modifications of this invention will be apparent to those
skilled in the art. For example, the concave curve in the blade
could be absent from the nontwisted central section of the blade
while still being present in the radially outermost twisted blade
portions. Thus, the scope of this invention is to be limited only
by the appended claims.
* * * * *